linux-kernel - Re: [PATCH] clk: don't call __of_clk_get_by_name() unnecessarily from clk

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Message-ID: <20180212210053.GO9418@n2100.armlinux.org.uk>
Date:   Mon, 12 Feb 2018 21:00:53 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     David Lechner <david@...hnology.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: [PATCH] clk: don't call __of_clk_get_by_name() unnecessarily
 from clk_get()

On Mon, Feb 12, 2018 at 02:51:57PM -0600, David Lechner wrote:
> On 02/12/2018 08:24 AM, Bartosz Golaszewski wrote:
> >From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> >The way this function is implemented caused some confusion when
> >converting the TI DaVinci platform to using the common clock framework.
> >
> >Current kernel supports booting DaVinci boards both in device tree as
> >well as legacy, board-file mode. In the latter, we always end up
> >calling clk_get_sys() as of_node is NULL and __of_clk_get_by_name()
> >returns -ENOENT.
> >
> >It was not obvious at first glance how clk_get(dev, NULL) will work in
> >board-file mode since we always call __of_clk_get_by_name(). Let's make
> >it clearer by checking if of_node is NULL and skipping right to
> >clk_get_sys().
> >
> >Cc: Sekhar Nori <nsekhar@...com>
> >Cc: Kevin Hilman <khilman@...libre.com>
> >Cc: David Lechner <david@...hnology.com>
> >Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >---
> >  drivers/clk/clkdev.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> >index 7513411140b6..f394e8964909 100644
> >--- a/drivers/clk/clkdev.c
> >+++ b/drivers/clk/clkdev.c
> >@@ -199,7 +199,7 @@ struct clk *clk_get(struct device *dev, const char *con_id)
> >  	const char *dev_id = dev ? dev_name(dev) : NULL;
> >  	struct clk *clk;
> >-	if (dev) {
> >+	if (dev && dev->of_node) {
> >  		clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
> >  		if (!IS_ERR(clk) || PTR_ERR(clk) == -EPROBE_DEFER)
> >  			return clk;
> >
> 
> Shouldn't you be sending this to the linux-clk mailing list and cc'ing
> the clock maintainers?

No, I'm the maintainer for clkdev, as per MAINTAINERS.

> FWIW, it seems pretty clear to me that if we are using a board file
> then we should expect clk_get_sys() to be called because there is
> no device tree.

clk_get() pre-dates DT, and using it has no bearing on whether DT is
in use or not.  The above change looks correct to me - if the
struct device is not a DT device, then we shouldn't be trying to look
up the clock in DT.

-- 
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